Elastic light scattering possesses several polarization properties that may be used follow the state of a virus in aqueous suspension, including such processes as assembly or disassembly, interaction with immune system agents, and interaction with synthetic drug molecules. These experiments fall into an area of optics known as "measurement of ?? Muller scattering matrix". The Muller matrix contains 16 independent quantities which may be measured as a function of scattering angle, so the data from these experiments comprises 16 curves of varying shape. For viruses and larger particles, these curves contain many distinctive features that are partially interpretable in terms of a priority model calculations, and which may be even more interpretable after correlation with electron microscopy. Measurement of the Muller matrix is a delicate experiment, and reliable published results are lagging behind theory at this point. We propose to build a Muller instrument, based on a new principle which we have recently worked out in detail. We shall use a Zeeman-effect laser as a polarization-modulated light source, together with crystal polarization optics of the highest quality, and extensive automatic correction of data for imperfections in alignment and degree of retardation. Virus samples will be drawn through the scattering region by electrophoretic mobility, providing simultaneously purification and also a degree of control over partial orientation, which doubles the amount of information that can be obtained. We shall extend our theoretical work along several lines: (i) Increase the number of subunits our modeling program can handle, to probe the properties of the transition region between granular models and continuous material. This will involve supercomputer calculations. (ii) Extend Muller matrix theory to include the dynamic perties that result in quasi-elastic light scattering. This should result in a theory which will allow measurement of certain gross mechanical properties of a virus particle, such as its response to shear forces in the liquid that supports it. (iii) Extend our analytic orientation averaging method to include partially oriented virus ensembles, as might be seen in electrophoretically moving samples. (iv) Treat the scattering of partially oriented viruses trapped near the focus of a laser beam, as a function of laser polarization.